The invention relates to a method and device for performing fluid influx tests in a wellbore traversing a permeable formation.
It is known from U.S. Pat. Nos. 4,860,581 and 6,330,913 to perform a fluid inflow test in a wellbore traversing a permeable formation by:    a) inserting a well test device comprising a straddle packer assembly into the wellbore such that the straddle packer assembly separates a test section from other sections of the wellbore; and    b) performing a fluid influx test during which the fluid pressure the test section is reduced, pore fluid is induced to flow from the pores of the permeable formation into the test section and fluid influx into the test section is monitored.
The known well test devices are usually used in wellbores that are filled with drilling mud using a downhole pump that works against the hydrostatic column to achieve so-called Low, reduced, or Zero shock sampling. The pumping is generally continued for a period of time, which is long enough to flush away drilling mud from the pores of the mud invaded zone of the formation in the vicinity of the test section of the wellbore.
The known well test devices are often used in exploration wells to obtain an early indication of the potential crude oil and/or natural gas production of an oil and/or natural gas containing formation surrounding the wellbore and if the well tests indicate that exploitable crude oil and or natural gas reserves are present formation samples are taken to assess in a laboratory which completion fluids are to be injected into the pores of the formation to stimulate crude oil and/or gas production and to inhibit skin effects due to reduced permeability of the formation surrounding the wellbore due to invasion of drilling mud and/or completion fluid.
It is an object of the present invention to provide a method and well test device for performing fluid influx tests in a wellbore traversing a permeable formation, which allow to test the compatibility of completion fluids in situ, without requiring taking of formation samples and testing these samples in a laboratory.